Mathematical Double Struck Capital I
U+1D540MATHEMATICAL DOUBLE-STRUCK CAPITAL IMathematical Alphanumeric Symbols
Also known as blackboard bold I
Copy and paste 𝕀. The Mathematical Double Struck Capital I character has Unicode code point U+1D540 and decimal HTML code 𝕀.
Symbol codes
- Unicode
U+1D540- HTML Code
𝕀- CSS Code
\1D540- HTML Entity
𝕀- HEX Code
𝕀
Technical properties
Unicode 18.0.0
- Code point
- U+1D540
- Decimal
- 120128
- Unicode name
- MATHEMATICAL DOUBLE-STRUCK CAPITAL I
- Block
- Mathematical Alphanumeric Symbols · U+1D400–U+1D7FF
- General category
- Uppercase Letter (Lu)
- Script
- Common
- Introduced
- Unicode 3.1
- JavaScript
- "\u{1D540}"
Appears in
About Mathematical Double Struck Capital I
𝕀 is encoded in Unicode as code point U+1D540 (decimal 120128). Its official Unicode name is MATHEMATICAL DOUBLE-STRUCK CAPITAL I.
It belongs to the Mathematical Alphanumeric Symbols block (U+1D400–U+1D7FF), its General Category is Uppercase Letter (Lu), and it was added in Unicode 3.1, released in 2001. Its script value is Common: it is shared across writing systems rather than belonging to one.
Sources: Unicode Character Database 18.0.0, the HTML Standard’s list of named character references, and Unicode’s code page mappings.
How to type or insert Mathematical Double Struck Capital I
- Any device
- Select Copy symbol, then paste with Ctrl+V, or ⌘+V on a Mac.
- Microsoft Word
- Type
1D540, then press Alt+X. - macOS Character Viewer
- Press Control+⌘+Space and search for “mathematical double-struck capital i”.
- Linux (GTK and IBus)
- Press Ctrl+Shift+U, type
1d540, then press Space. - HTML
𝕀or𝕀. In a UTF-8 page you can also paste the character itself.- CSS
content: "\1D540";in a::beforeor::afterrule.- JavaScript
"\u{1D540}"
Common questions about Mathematical Double Struck Capital I
What is the Mathematical Double Struck Capital I symbol?
𝕀 (Mathematical Double Struck Capital I) is an uppercase letter in Unicode’s Mathematical Alphanumeric Symbols block. Its code point is U+1D540, and it has been part of the standard since Unicode 3.1 (2001). It is also known as blackboard bold I.
How do I copy and paste the Mathematical Double Struck Capital I symbol?
Select Copy symbol at the top of this page, then paste with Ctrl+V on Windows and Linux or ⌘+V on a Mac. On a phone, tap Copy symbol, then touch and hold where you want it and choose Paste. 𝕀 pastes as ordinary text, so it works in documents, messages, and code.
How do I type the Mathematical Double Struck Capital I symbol on Windows?
In Microsoft Word, type 1D540 and press Alt+X to turn the code into 𝕀. In other apps, the quickest way is to copy it from this page.
How do I type the Mathematical Double Struck Capital I symbol on a Mac?
Press Control+⌘+Space to open the Character Viewer, search for “mathematical double-struck capital i”, and double-click the result to insert it.
How do I type the Mathematical Double Struck Capital I symbol on an iPhone or Android phone?
The simplest way is to copy it from this page and paste it where you need it. If you use it often, save it as a text shortcut: on iPhone, go to Settings > General > Keyboard > Text Replacement; with Gboard on Android, go to Gboard settings > Dictionary > Personal dictionary.
Can I use the Mathematical Double Struck Capital I symbol in Word, Google Docs, and social media?
Yes. 𝕀 is a standard Unicode character, so you can paste it into Microsoft Word, Google Docs, emails, and posts or bios on Instagram, X, Facebook, and TikTok. In Google Docs you can also choose Insert > Special characters and search for “mathematical double-struck capital i”. In Word, choose Insert > Symbol > More Symbols, set from to Unicode (hex), and enter 1D540 as the character code.
Is the Mathematical Double Struck Capital I symbol an emoji?
No. 𝕀 is a text symbol, not an emoji. It takes the color and size of the surrounding text, and its exact shape depends on the font.
Why does the Mathematical Double Struck Capital I symbol show as a box or question mark?
An empty box or a question mark means the font on that device has no glyph for 𝕀. The character is still there: it appears correctly wherever a font covers Unicode’s Mathematical Alphanumeric Symbols block, and free font families such as Google Noto cover nearly all of Unicode.
What are the HTML and CSS codes for the Mathematical Double Struck Capital I symbol?
In HTML, write 𝕀 (decimal) or 𝕀 (hexadecimal), or the named entity 𝕀. In CSS, use content: "\1D540"; in a ::before or ::after rule, and in JavaScript "\u{1D540}". See all HTML codes.